In this research, a low-cost template-based process has been developed to structure the surfaces of polymeric materials rendering them superhydrophobic. This biology-inspired approach was developed using results from the first part of this thesis: the first known detailed study of superhydrophobic aspen leaf surfaces. Aspen leaves, similar to lotus leaves, possess a dual-scale hierarchical surface structure consisting of micro-scale papillae covered by nano-scale wax crystals, and this surface structure was used as a blueprint in the structuring of templates. These distinctive surface features coupled with a hydrophobic surface chemistry is responsible for these leaves’ extreme non-wetting property. Non-wetting is further augmented by the unique high aspect ratio aspen leafstalk geometry. The slender leafstalks offer very little resistance to twisting and bending, which results in significant leaf movement in the slightest breeze, facilitating water droplet roll-off. The structured template surfaces, produced by sand blasting and chemical etching of electrodeposited nanocrystalline nickel sheets, resemble the negative of the superhydrophobic aspen leaf surfaces. Re-usable templates were subsequently employed in a hot embossing technique where they were pressed against softened polymers (polyethylene, polypropylene and polytetrafluoroethylene) thereby transferring their surface structures. The resulting pressed polymer surfaces exhibited features very similar to aspen leaf surfaces. This process increased the water contact angle for all pressed polymers to values above 150 degrees. Additionally, after pressing the water roll-off angle for all polymer surfaces dropped below 5 degrees. The effects of water surfactant concentration, water drop size and temperature on the wetting characteristics of the structured polymers were studied to indicate in which applications these functional surfaces could be most beneficial. Coupling this attractive superhydrophobic surface property with mechanical motion (shaking, bending, or vibrating) could result in superhydrophobic surfaces with superior non-wetting properties suitable for a wide range of applications.

In this research, a low-cost template-based process has been developed to structure the surfaces of polymeric materials rendering them superhydrophobic. This biology-inspired approach was developed using results from the first part of this thesis: the first known detailed study of superhydrophobic aspen leaf surfaces. Aspen leaves, similar to lotus leaves, possess a dual-scale hierarchical surface structure consisting of micro-scale papillae covered by nano-scale wax crystals, and this surface structure was used as a blueprint in the structuring of templates. These distinctive surface features coupled with a hydrophobic surface chemistry is responsible for these leaves’ extreme non-wetting property. Non-wetting is further augmented by the unique high aspect ratio aspen leafstalk geometry. The slender leafstalks offer very little resistance to twisting and bending, which results in significant leaf movement in the slightest breeze, facilitating water droplet roll-off. The structured template surfaces, produced by sand blasting and chemical etching of electrodeposited nanocrystalline nickel sheets, resemble the negative of the superhydrophobic aspen leaf surfaces. Re-usable templates were subsequently employed in a hot embossing technique where they were pressed against softened polymers (polyethylene, polypropylene and polytetrafluoroethylene) thereby transferring their surface structures. The resulting pressed polymer surfaces exhibited features very similar to aspen leaf surfaces. This process increased the water contact angle for all pressed polymers to values above 150 degrees. Additionally, after pressing the water roll-off angle for all polymer surfaces dropped below 5 degrees. The effects of water surfactant concentration, water drop size and temperature on the wetting characteristics of the structured polymers were studied to indicate in which applications these functional surfaces could be most beneficial. Coupling this attractive superhydrophobic surface property with mechanical motion (shaking, bending, or vibrating) could result in superhydrophobic surfaces with superior non-wetting properties suitable for a wide range of applications.

Small angle x-ray scattering (SAXS) with synchrotron radiation was used to characterize nano-sized voids in different nominally pure aluminum (Al) alloys produced by quenching. The scattering signal from nano-voids is shown to be predictable from SAXS theory, and the information related to the void population confirm past experiments and reveal new details about quench-void formation in Al. Specifically, voids were produced in 99.97 at.% to 99.9994 at.% Al alloys by infrared heating to 450 – 625 °C followed by controlled rapid quenching at 10^3 to 10^5 °C/s. For changing processing conditions, the size of voids varied between 5 to 11 nm, and the density of voids varied by over an order of magnitude. Results from SAXS were consistent with TEM observations performed on the same specimens, indicating that synchrotron SAXS can be reliably used to characterize nano-voids produced in quenched Al. Factors determined to affect voids were consistent with previous studies, except that the present nano-voids dissolved after only 3 min. at 145 °C, indicating that quenched nano-voids are less stable than previously determined. SAXS also showed that void size is sensitive to quench temperature and quench rate. The activation energies for void nucleation and growth were determined to be 0.75 ± 0.10 and 0.19 ± 0.03 eV/at., respectively, confirming that hydrogen and di-vacancies take part in nucleation and growth during quenching. It was concluded that the non-linear tail of the quench curve plays a crucial role in void formation, and that voids form when long range diffusion is inhibited. This information can be utilized to design new Al alloys that limit incipient void formation, which is detrimental to properties such as formability. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2008-04-25 15:17:30.211 / Natural Sciences and Engineering Research Council of Canada; General Motors of Canada Limited

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Integrated circuit (IC) technology has evolved rapidly but the continual development of transistors and interconnects (the connection between the transistors) is facing greater and greater challenges, which require new materials and new processes. Research in nano-particles (or nanoscale clusters) creates possibilities for both new materials and new processes. This thesis explores the electrical properties of amorphous antimony clusters and develops a new copper cluster deposition technique for application to transistors and interconnects respectively. For amorphous antimony clusters, an electron diffraction technique was applied to identify the phase of the clusters prior to deposition on electrically contacted samples. The deposition process produced uniform cluster films suitable for electrical measurements. A consistent percolation exponent for conduction (t=1.85) was obtained. After deposition, the resistance of the films continued to increase because of coalescence. Although it was previously reported that amorphous antimony films were semiconducting, from linear I(V) curves, a low temperature coefficient of resistance (10⁻⁴ K⁻¹) and no observable gate effect, it was found that the antimony cluster films in this study were not semiconducting, possibly due to the effect of coalescence. The development of the copper clusters for the interconnects application was very successful. Trenches of sub-200 nm widths, with different diffusion barriers and seed layers, and up to 5:1 aspect ratios have been completely filled with copper clusters. Due to the propensity for reflection of clusters from the planar surfaces between trenches, the process results in selective deposition into the trenches and bottom up filling is demonstrated. After annealing in hydrogen or in vacuum, the clusters sinter into a copper seed layer. The resistivity measured by a thin film four-point probe (1.6 - 2.3 × 10⁻⁸ Ωm) meets the requirement by industry (2.2 × 10⁻⁸ Ωm). The process is therefore promising for industrial application, but further testing and investigation of integration issues is required.

The subject of this thesis is microwave assisted rapid growth of ZnO nanoparticles from an aqueous solution using different zinc precursors and heating powers, and characterization of these by scanning electron microscopy, atomic force microscopy and optical microscopy. The goal of the experiment performed was to study the effect of the heating power of the microwave oven as well as that of the zinc precursor used on the morphology and size of the grown particles. ZnO nanoparticles has many interesting possible applications in a wide range of areas, such as LED-technology, medicine, antibacterial applications, solar cells and more. Also, there is still a lot of knowledge missing concerning the growth mechanisms and properties of ZnO on the nano-scale. These two facts give good reasons to continue the research and investigations of nano-ZnO. Being able to use the microwave assisted growth method in large scale is highly interesting as it is relatively cheap, safe and easy compared to other presently used methods, so there are good reasons to learn more about this technique as well. In this project it was found that both the heating power and the zinc precursor used had significant effects on the morphology and size of the grown ZnO nanocrystals, and also that adding a zinc seed layer to the surface of the substrate before growth made a big difference in some cases.

<p>The ability to interrogate structure-function photophysical properties on lanthanide-doped nanoscale materials will define their utility in next-generation applications and devices that capitalize on their size, light-conversion efficiencies, emissive wavelengths, syntheses, and environmental stabilities. The two main topics of this dissertation are (i) the interrogation of laser power-dependent quantum yield and total radiant flux metrics for a homogeneous, solution phase upconversion nanocrystal composition under both continuous wave and femtosecond-pulsed excitation utilizing a custom engineered absolute measurement system, and (ii) the synthesis, characterization, and power-dependent x-ray excited scintillation properties of [Y₂O₃; Eu] nanocrystals, and their integration into a fiber-optic radiation sensing device capable of in vivo dosimetry.</p><p>Presented herein is the laser power-dependent total radiant flux and absolute quantum yield measurements of homogeneous, solution-phase [NaYF₄; Yb (15%), Er (2%)] upconversion nanocrystals, and further compares the quantitative total radiant flux and absolute quantum yield measurements under both 970 nm continuous-wave and 976 nm pulsed Ti-Sapphire laser excitation (140 fs pulse-width, 80 MHz). This study demonstrates that at comparable excitation densities under continuous-wave and fs-pulsed excitation from 42 - 284 W/cm<super>2</super>, the absolute quantum yield, and the total radiant flux per unit volume, are within a factor of two when spectra are integrated over the 500 - 700 nm wavelength regime. This study further establishes the radiant flux as the true unit of merit for quantifying emissive output intensity of upconverting nanocrystals for application purposes, especially given the high uncertainty in solution phase upconversion nanocrystal quantum yield measurements due to their low absorption cross-section. Additionally, a commercially available bulk [NaYF₄; Yb (20%), Er (3%)] upconversion sample was measured in the solid-state to provide a total radiant flux and absolute quantum yield standard. The measurements were accomplished utilizing a custom-engineered, multi-detector integrating sphere measurement system that can measure spectral sample emission in Watts on a flux-calibrated (W/nm) CCD-spectrometer, enabling the direct measurement of the total radiant flux without need for an absorbance or quantum yield value. </p><p>Also presented is the development and characterization of a scintillating nanocrystalline composition, [Y_2-xO₃; Eu_x, Li_y], in which Eu and Li dopant ion concentrations were systematically varied in order to define the most emissive compositions under specific x-ray excitation conditions. It is shown that these optimized [Y_2-xO₃; Eu_x, Li_y] compositions display scintillation responses that: (i) correlate linearly with incident radiation exposure at x-ray energies spanning from 40 - 220 kVp, and (ii) manifest no evidence of scintillation intensity saturation at the highest evaluated radiation exposures [up to 4 Roentgen per second]. X-ray excitation energies of 40, 120, and 220 kVp were chosen to probe the dependence of the integrated emission intensity upon x-ray exposure-rate in energy regimes where either the photoelectric or the Compton effect governs the scintillation mechanism on the most emissive [Y_2-xO₃; Eu_x, Li_y] composition, [Y_1.9O₃; Eu_0.1, Li_0.16]. These experiments demonstrate for nanoscale [Y_2-xO₃; Eu_x], that for comparable radiation exposures, when scintillation is governed by the photoelectric effect (120 kVp excitation), greater integrated emission intensities are recorded relative to excitation energies where the Compton effect regulates scintillation (220 kVp excitation). </p><p>The nanoscale [Y_1.9O₃; Eu_0.1, Li_0.16] was further exploited as a detector material in a prototype fiber-optic radiation sensor. The scintillation intensity from a [Y_1.9O₃; Eu_0.1, Li_0.16]-modified optical fiber tip, recorded using a CCD-photodetector or a Si-photodiode, was correlated with radiation exposure using a Precision XRAD 225Cx small-animal image guided radiation therapy (IGRT) system, an orthovoltage cabinet-irradiator, and a clinical X-ray Computed Tomography (CT) machine. For all x-ray energies tested from 80 - 225 kVp, this near-radiotransparent device recorded scintillation intensities that tracked linearly with total radiation exposure, highlighting its capability to provide alternately accurate dosimetry measurements for both diagnostic imaging and radiation therapy treatment. Because Si-based CCD and photodiode detectors manifest maximal sensitivities over the emission range of nanoscale [Y_1.9O₃; Eu_0.1, Li_0.16], the timing speeds, sizes, and low power-consumption of these devices, coupled with the detection element's linear dependence of scintillation intensity with radiation dose, demonstrates the opportunity for next-generation radiation exposure measuring devices for in/ex vivo applications that are ultra-small, inexpensive, and accurate.</p> / Dissertation

This thesis is about "nano-cellular" polymer foams, i.e., to understand nano-bubble nucleation and growth mechanisms, we used Self-Consistent Field Theory(SCFT) for the research.\\ Classical Nucleation Theory (CNT) is often used to calculate nucleation rates, but CNT has assumptions which break down for a nano-sized bubble: it assumes planar sharp interfaces and bulk phases inside bubbles. Therefore, since the size of a nano-sized bubble is comparable to the size of the polymer molecule, we assumed that a bubble surface is a curved surface, and we ivestigated effects of curvature on the nucleation barrier. SCFT results show that sharper curvatures of smaller s cause a higher polymer configurational entropy and lower internal energy, and also the collapse of the bulk phase for smaller bubbles causes low internal energy. Consequently, the homogenous bubble nucleation barrier for curved surfaces is much smaller than flat surface (CNT prediction).\\ We calculated direct predictions for maximum possible cell densities as a function of bubble radius without calculation of nucleation barrier or nucleation rates in CNT. Our results show higher cell densities at higher solvent densities and lower temperatures. Moreover, our cell density prediction reveals that rather than surface tension, the volume free energy, often labelled as a pressure difference in CNT, is the dominant factor for both cell densities and cell sizes. This is not predicted by CNT.\\ We also calculated direct predictions for the maximum possible cell densities as a function of system volume in compressible systems. With an assumption that system pressure has an optimal pressure which gives the maximal density of good quality foams (bulk phase inside bubble), we calculated the inhomogeneous system pressure, the homogeneous system, and cell density as a function of system volume.\\ Maximal cell prediction in compressible system shows the incompressible system prediction is the upperbound maximal cell density, and qualitatively consistent with the compressible system results - higher cell densities at low temperatures and high solvent densities.\\ In addition, our results show a bigger expansion as well as a high cell density at low temperature and high solvent density, but temperature is a more dominant factor than the solvent density. From our results, we assume that a quick pressure dropping is required to get a better quality foam of a higher cell density.

The restrictions of micro-scale systems are approaching rapidly. In anticipation of this development, nano-scale electronics has become the focus of many researchers and engineers in academia and industry since early 1990s. The basic building blocks of modern integrated circuits have been diodes and transistors with their current-voltage I-V characteristics being of prime significance for the design of complex signal processing and shaping devices and systems. Classical and semi-classical physical principles are no longer powerful enough or even valid to describe the phenomena involved. The application of rich and powerful concepts in quantum theory has become indispensable. These facts have been influential in undertaking this research project. This research is built upon the determination of the Eigenpairs of one and two dimensional positive differential operators with periodic boundary conditions. The Schrödinger equation was solved for positive operators in both one and two dimensions. Fourier series were used to express the derivatives as the summation of Fourier terms. This led to a novel approach for the calculation of the eigenmodels of a perturbed potential well. The perturbation can be done via an electric field applied to the potential well. The research in this thesis includes a thorough understanding of quantum mechanics fundamentals, mastering of different approximation techniques such as the variational technique and results that have been generated and published using the novel techniques.